Note that it's currently the only comment from that user, and the username looks like a random throwaway (unless vb6sp6 is a big fan of Visual Basic 6.0, Service Pack 6).
But maybe it's an obvious guess to a wide number of people with knowledge of that general ecosystem of companies.
I'm guessing it was someone within Verizon up-stream, given they were thrown under the bus. They'd know who was to blame, would potentially resent their employer being linked, and could pass off their comment as a guess if pressured.
That's plausible. But it also could be a good guess. Lots of messages from valentines day gives us a good hint that we have a time capsule from february. Machine with time capsule reboots and then sends everything is plausible for SMS systems (smtp too).
No strong carrier affiliation for senders or receivers suggests an intermediary. Not a lot of those in the US; Syniverse, maybe SAP (Sybase 365); I don't think Bandwidth does intercarrier work.
